Use an area to evaluate
∫ 3x dx,
where a > 1
Having some trouble with this, could someone explain to me how to do this?
No, it is not. Go back and do what Sudharaka said!
What are the coordinates of the vertices of the trapezium (I would say "trapezoid")? What is the "height" of that trapezoid? What are the lengths of the two "bases" of the trapezoid? Do you know the formula for the area of a trapezoid?